Tectonic and climatic signals from apatite detrital fission-track analysis of the Cape Robert Project core records, south Victoria Land, Antarctica.

The Cenozoic tectonic reorganization of the West Antarctic Rift System in the Ross Sea region occurred concurrently with a major change in the global climate system and a global reorganization of plate motions. This region thus provides the opportunity to study in detail a range of geological issues dealing with tectonic and climate feedbacks during the late Eocene/early Oligocene greenhouse/icehouse transition at high latitudes. With the aim to decipher tectonic vs. climatic forcing in the ice sheet drainage evolution, a detrital apatite fission track study was carried out throughout the Cenozoic drill-cored stratigraphic succession of the Cape Roberts Project (McMurdo Sound, Victoria Land Basin). Apatite fission-track ages of detrital samples, with depositional ages between 34 Ma and 17 Ma, were decomposed into statistically significant age populations. Three age peaks were detected, reflecting different bedrock provenance areas: (i) a young peak (P1 between 34 Ma and 26 Ma) recording the signal of a source area exhumed with a constant denudation rate, but absent in the proximal continental area; and (ii) two peaks, older than 40 Ma, that are instead compatible with thermochronological data available from the onshore bedrock. P1 peak testifies a late Oligocene-early Miocene denudation event and traces a southern provenance of a fraction of the sediments filling the Cape Roberts Basin. We propose that this denudation event might have been triggered by renewed N-S transtensional shearing along the western shoulder of Victoria Land Basin, controlling glacial flow pattern and the associated sediment transport.